Almost all lighting apparatuses currently available on the market produce illumination of approximately the same colour, daylight (white colour) or warm daylight (slightly yellowish colour). When a different colour is required it occurs using filters and colour coatings.
Light-emitting diodes (LEDs) typically emit illumination or light of a single predetermined colour, although LEDs emitting a variety of colours exist. Colour music devices for example use a large number of LEDs emitting light of different colours to produce variable or constant colour illumination. However, the colours produced cannot be mixed to produce a colour continuum and in order to generate illumination of the desired power light emitted by a large number of LEDs has to be collected. The size of such a light sources is relatively large since the LEDs have to be distributed over the surface of an outlet opening of the illumination source.
Different types of reflectors or illumination concentrators including conical, spherical, and aspherical are used to collect and concentrate the light emitted by a plurality of LEDs onto the smaller area of the outlet opening. However, analyses show that such concentrators collect at maximum 5% of the light flux emitted by a plurality of LEDs or other light sources.
LEDs containing a number of emitters in one common package, each emitting light of different colour are know, they cannot, however, be operated simultaneously, nor do they allow colour mixing to produce a continuum of colours. They usually produce a low luminous flux. There are however no illumination apparatuses of relatively small size, capable of producing white light and varying colours and intensities of illumination flux, and concentrating the emitted flux on a relatively small surface or a line.